Nervous System Part 3: Special Senses Flashcards
what are the five special senses?
vision, taste, smell, hearing and equilibrium
what are the outer fibrous layer made of?
sclera and cornea
the posterior portion of the eye
aka “white of the eye”
the sclera
anterior part of the eye
transparent part where light enters
cornea
fills space btw the cornea and lens
aqueous humor
what does the middle layer of the eye include?
the ciliary muscle, choroid and iris
darkly colored and posterior to the eye
prevents light from dispersing throughout eye
highly vascular and supples blood to other layers of the eye
choroid
changes shape of the lens allowing it to focus
ciliary body
anterior to the ciliary body that contains a colored part of the eye
controls the amount of light let into the pupil
uses muscle fibers to contract or dilate based on amount of light in environment
iris
a hole in the center of the iris
pupil
the inner sensory layer includes what?
retina
contains 2 photoreceptors called rods and cones
retina
cells sensitive to light
photoreceptors
operate in bright light
help to see sharp COLORFUL images
cones
stimulated in dim light and are more numerous
rods
located posterior to iris and pupil
lens
chamber filled w/ vitreous fluid
vitreous body
helps to hold retina firmly to choroid
vitreous fluid
vision pathway
light passes into eye through the cornea, aqueous humor, lens, and vitreous humor to the posterior surface of the eye on the retina
photoreceptors in retina sign optic nerve on optic chiasm where optic tracts are made and terminate at the LGN
light info continues from thalamaus via optic radiations to primary visual area of occipital lobe to interpret as vision
are signaled by photoreceptors in the retina when light comes in to pass to optic chiasam
optic nerve
located at the base of the hypothalamus
fibers of the optic nerve cross to the other side when they reach here to form optic tracts
optic chiasm
formed when optic nerves cross at optic chiasm
terminate in thalamus at the lateral geniculate nucleus (LGN)
optic tracts
field closest to the nose
nasal visual field
located on later side of eye
peripheral vision field
Overlapping information in the nasal visual fields allows for 3-D vision
binocular visual field
turns eye mediall
medial rectus
turns eye medially
innervated by the oculomotor nerve
medial rectus
eye medially and elevates it
innervated by the oculomotor nerve
superior rectus
responsible fo eye elevation, lateral movement and external rotation
innervated by the oculomotor nerve
inferior oblique
fifth muscle that is controlled by the trochlear nerve
responsible for eye depression, lateral movement and internal rotation
superior oblique
moves the eye medially and depresses it
innervated by the oculomotor nerve
inferior rectus
controlled by abducens nerve and turns the eye laterally
lateral rectus
lenses that slowly become hardened and cloudy over time
make vision look blurry b/c light is unable to enter
cataracts
caused by damage to the abducens nerve
aka double vision
test is look left and right
diplopia
consists of the auricle and external acoustic canal (meatus)
external ear
shaped to funnel sound waves into the external acoustic canal so that sounds can be detected
made of cartilage covered with thin skin
auricle
elastic cartilage covering auricle
helix/rim
he tunnel between the auricle and tympanic membrane
becomes a cylinder through the temporal bone
external acoustic meatus
The canal is lined with skin containing hairs and glands that secrete this
trap foregin materials and acteria
cerumen (Earwax)
inner end of the ear canal ends here
a thin membrane of connective tissue whose vibration transmits sound energy to the middle ear
tympanic membrane (eardrum)
is an air-filled chamber containing the ossicles
middle (tympanic cavity)
the malleus (hammer), incus (anvil), and stapes (stirrup)
smalles bones in the body
ossicles
receives the vibrations from the eardrum and transfers them along through the incus
malleus
conveys vibrations to the inner ear
stapes
composed of the bony and membranous labyrinths filled with fluid
inner ear
connects to the 3 semicircular canals that house receptors to provide the bodys vestibular system
vestibule
equilibrium and balance
vestibular system
occurs from damage to the nerve pathway, specifically, the receptor cells or cochlear nerve that transmit them to brain
can be partial or complete in one or both ears
nerve deafness
occurs from damage to outer or middle ear
not complete deafness b/c sound waves can be conducted through cranial bones to organ of Corti
i.e buildup of earwax can block sound waves
ossicles fuse, decreasing vibrations
conduction deafness
Damage to the auditory pathway results in hearing loss
can be partial or total
deafness
divided into three sections: the vestibule, semicircular canals, and cochlea
bony lambyrinth
filled with fluid that contain equilibrium receptors that cause action potentials in response to motion (head movements or rotation)
action potentials are sent thorugh vestibular part of cranial nerve 8
contribute to vestibular sense
semicircular canals
spiral, bony chamber containing membranous endolymp filled cochlear duct
house the organ of corti and terminates at cochlear nerve
cochlea
is the sense organ for the auditory system
contains the tectorial membrane and tiny hairs called stereocilia
organ of Corti
moves and bends stereocilia whne the fluid in the cochlear duct receive vibrations
tectorial membrane
moves and bends stereocilia whne the fluid in the cochlear duct receive vibrations
tectorial membrane
are bipolar receptor cells found in the olfactory epithelium on the roof of the nasal cavity
travel through the ethmoid bone in a location called the cribriform plate
olfactory nerves
is a special sense and is one of the chemical senses.
receptors are activated by airborne chemical substances dissolved in fluid on nasal mucous membranes
smell/olfaction
paired masses of gray matter where olfactory nerve axons synapse with other cell bodies of the olfactory pathway
olfactory bulbs
formed when axons travel together from the olfactory bulbs
carry info to temporal lobes
signals are interpreted here in the primary olfaction area as smell
olfactory tracts
defined as a combination of a limited number of primary odors that are detectable by the brain.
smell
seven primary odors are
floral (roses), ethereal (dry-cleaning fluid), camphorates (mothballs), musky (perfumes), peppermint (mint gum), pungent (vinegar) and putrid (rotten eggs)
responsible for the special sense of taste
gustatory system
is one of the chemical senses because its receptors are activated by chemical substances dissolved in saliva
taste (Gustation)
are inside taste buds mostly on the tongue but are also throughout the mouth and throat
taste receptors
responsible for gripping food and repositioning it between the teeth, forming a bolus
tongue
compact mass made by food gripped by the tongue
bolus
part of the tongue located anteriory
apex
attached to the floor of the posterior surface of the mouth.
root
located on the inferior surface of the tongue along the midline
frenulum
raised bumps on the tongue
papillae
3 ypes of papillae that help to grip food on the tongue
circumvallate, fungiform and fiiform
contain chemical receptors that are stimulated by the chemical composition of food
found on the tongue and wall of pharnyx
formed by gustatory cells and supporting cells
taste buds
form the bulk of the taste bud and separate the taste receptors cells from one another.
supporting cells
are the chemoreceptor cells inside the taste buds
each one terminates in a gustatory hair that projects into saliva to detect chemical
gustatory cells
serve as stem cells, which divide and differentiate into new supporting cells that then form new gustatory cells.
basal cells
as food chemicals contact the gustatory hairs, which generate an action potential in dendrites that are wrapped around the gustatory cells
he nerve impulse is carried by afferent fibers through two cranial nerve pairs, the facial nerves, and the glossopharyngeal nerves
transmit impulses to thalmaus to the parietal lobe to be interpreted as taste
taste pathway
what are the 5 primary tastes:
sweet, sour, salty, bitter savory (umami)
loss of smell
can also happen in the case of a growing brain tumor that blocks the olfactory pathway
anosmia
sounds like insomnia
loss of sensation of taste
When the olfactory receptors are obstructed by nasal congestion or other factors, the sensation of taste is dulled or completely lost.
ageusia
think gustatory
